Dave Greenberg and Donald Lobo started CiviCRM after working together at Groundspring.org. Groundspring.org provided donation and email tools for nonprofits and merged with Network for Good in 2005. Lobo also comes from Yahoo! in its early years before his work at Groundspring. Through their work at Groundspring, they realized there was a need for an open source tool in the nonprofit/NGO arena and began the CiviCRM project around 2004.
One of the reasons CiviCRM was designed to be open source is partially out of pragmatism: to meet the ambitious goal of serving the CRM needs of NGO groups across the globe, the tool needed to be flexible enough to be customized to a widely ranging set of needs. Because the goal was to support such a big sector rather than turn a profit, the founders and core team opted to rely on the smart people supporting these organizations to actually contribute to development rather than to provide a single catchall tool that would serve everyone's needs.
Because CiviCRM as a contact relationship management tool built specifically for the civil society or nonprofit sector is one of its kind, CiviCRM community has contributors and users all over the world.
There are a few core developers on the Civi team including Dave and Donald (who goes by his last name, Lobo), Tim and Coleman, all based in the US; Yashodha, Kurund, Deepak in India; and Michael who is based in the UK as listed on the core team page. There is also a peripheral ring of heavy contributors that have been part of the community for a long time from the US, Canada, New Zealand, India, and parts of Europe. A visitor to the CiviCRM website can see a rotating set of pictures of ongoing contributors to the community along the top of the page. This gives a visual sense of the diversity of the community and of the organizations and projects that CiviCRM supports. A large list of contributors is also thanked publicly on the website.
A sampling of organizations where CiviCRM is operating shows the adaptability of the tool: consider the differences between the New York State Senate, a housing organization in the Netherlands called De Goede Woning, the Missouri Credit Union Association, and the Irish Association of Massage Therapists.
Measurements from 2007 of community size show that active online registrations to CiviCRM sites had grown to 935 and that CiviCRM installations were at 4500. Both figures are certainly much bigger 6 years later, but I couldn't find updated numbers.
CiviCRM uses the GNU AGPL license as seen on the bottom of the demo page.
It must be built on top of a content management system, but users can choose between Drupal, Joomla, and Wordpress. The choice to expand to Wordpress is recent, but allows for more rapid installation and set-up given the wider use of Wordpress and relatively lower cost of maintaining a Wordpress site.
The documentation itself has a more comprehensive history than the project, or at least one that's easier to find. It is built using Floss Manuals, which is an open source tool for documenting open source projects. The commitment to open source tools is pervasive in the CiviCRM community, so in spite of a lack of public explanations about why CiviCRM was designed to be open source, the philosophical bent of the project is largely open.
Other tools used by the project are a combination of proprietary and open. The JIRA issue tracker is proprietary, for example. Drupal, Joomla, and Wordpress are all open source tools.
added Comments Thomas 11/6/2013 (see commit description)